Precast concrete silo complex and a method of constructing it

ABSTRACT

A precast concrete silo complex and a method of constructing it, in which quarter-cylindrical precast concrete members, constituting unit members, are each provided with a pair of radially protruding couplings near both the ends of the member, and the unit members are arranged to form unit cylinders. The unit cylinders are arranged lengthwise and crosswise, with the couplings facing the couplings of adjacent unit cylinders for defining a coupling space between each two adjacent unit cylinders. Horizontal clamp rods extend through the coupling spaces between the end portions of the unit members and between the couplings, and concrete is provided in the coupling spaces. The horizontal clamp rods are tensioned to clamp the end portions of the unit members and the couplings, to give prestress to the concrete, thereby combining the adjacent unit cylinders and solidifying the unit cylinders arranged lengthwise and crosswise. The unit members are joined vertically by mortar, and vertical clamp rods extend vertically set the unit members and are prestressed to apply prestress to the assembled unit cylinders, solidifying the complex vertically. Thus silo cylinders having a desired height are provided which are solidified lengthwise and crosswise, and which the inside of the silo cylinders constitute the main silo spaces and the spaces formed among the adjacent silo cylinders constitute sub silo spaces.

BACKGROUND OF THE INVENTION

The present invention relates to a precast concrete silo complex and a method of constructing it. Recently, high quality voluminous silos have been required for storing cereal grains, various raw materials, fodder, etc, and especially silos for grains are required to be highly airtight and structurally safe. As a method of constructing such silos, conventionally, the sliding form method has been considered the best. With the sliding form method, about 1.2 m high inside and outside molds are fixed by a frame called a yoke, and while said molds are raised upward at about 30 cm per hour by a hydraulic jack fitted to said yoke, concrete is poured continuously. In other words, concrete placing and mold releasing occur simultaneously so that a monolithic silo cylinder is produced. This method, compared with the successive concrete placing method makes it possible to obtain high airtightness which is the most important for grains (especially for imported grains) and provides a beautiful appearance, and therefore has been considered the best method as mentioned above. However, while this method can shorten the period of construction, the necessity of working day and night for a short period of time requires working in two or three shifts, and therefore requires many workers and engineers at one time, involving the difficulty of obtaining an adequate working force. In addition to this disadvantage in work control, according to this method, since concrete is directly poured in the field, the quality of the silo cylinder depends upon such natural conditions as weather at the time of pouring, and especially in the rainy or dry season, the quality is greatly affected. Furthermore, the quality control of the concrete itself is very difficult, causing indefinite factors in the quality such as airtightness and strength, which are important for the silo cylinder, which is a further large disadvantage of this method.

SUMMARY OF THE INVENTION

According to the present invention, silo cylinders are constructed by using precast concrete members, as unit members, the forming of which can be controlled exactly and properly under all conditions so as to control the quality of concrete by controlling such aspects as mixing of the concrete, arrangement of reinforcing bars, way of pouring and curing, and which members therefore have high dimensional accuracy and uniform quality. For this reason, the quality of the silo cylinders it not affected by such natural conditions as weather during construction and many workers are not required at one time for execution of the construction, enabling the construction to be executed at a constant work volume and constant work force, and facilitating the control. Particularly, the present invention uses precast concrete members as unit component members to construct silo cylinders arranged lengthwise and crosswise in a silo complex with said silo cylinders as main silo means and the spaces formed among the respectively adjacent silo cylinders as sub silo means. In this case the lengthwise, crosswise and vertical joining of said unit members is made very reasonably, and such lengthwise, crosswise and vertical reasonable structure is given prestress to substantially solidify the lengthwise and crosswise arranged silo cylinders. In other words, these silo cylinders have a very high strength in the silo complex with structural and dynamic solidification greater than the silo cylinders obtained by solid concrete pouring by a method such as said sliding form method. The present invention is described below in detail based on examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial perspective general view of the silo complex according to the present invention;

FIG. 2 is an enlarged perspective view of one of the unit members thereof;

FIG. 3 is a partial plan view for illustrating the process of construction of the silo complex;

FIG. 4 is an enlarged plan view of a connection among four unit members assembled as in FIG. 3;

FIG. 5 is a sectional view on line X--X of FIG. 4;

FIG. 6 is a sectional view on line Y--Y of FIG. 4 in an erected silo cylinder, with the portions in the circles illustrated on an enlarged scale;

FIGS. 7 (a)-(d) are sectional views on line Z--Z of FIG. 4 showing successive steps in joining the horizontal joints;

FIGS. 8 (a)-(d) are sectional views of successive steps in moving scaffolding frames; and

FIGS. 9 (a) and (b) are sectional view of steps in moving scaffolding frames.

DETAILED DESCRIPTION OF THE INVENTION

The basic unit member 1 of the silo complex of the present invention is a quarter-cylindrical precast concrete member 2 as shown in FIG. 2, provided with a pair of radially protruding couplings 3 as high as the member 2 and located near the ends e of the member 2. Said unit members 1 are assembled horizontally and vertically to form a unit cylinder t, and said unit cylinder t and adjacent unit cylinders t' are arranged lengthwise and crosswise in the silo complex as shown in FIG. 1, with the couplings 3 opposed to couplings 3' on the adjacent unit cylinders t', thereby forming a coupling space J between each two adjacent unit cylinders t and t' surrounded by the opposed two pairs of couplings 3 and 3' and by the end portions 4 and 4' between said couplings 3 and 3' and the respective ends of the members 2. Horizontal clamp rods 5 are mounted across said coupling spaces J between opposite end portions 4 and 4' and rods 6 are mounted across said spaces J between said couplings 3 and 3' on adjacent unit members 1, as shown in FIG. 4, and conrete 7 is placed in said coupling spaces. Spaces a are left between the opposed couplings 3 and 3' and the end portions 4 and 4'. Horizontal rods 5 and 6 are then tensioned to connect adjacent unit cylinders t and t', solidifying the lengthwise and crosswise arranged unit cylinders t and t', . . . Such tensioning of the horizontal rods 5 and 6 prestresses said concrete 7 and is done when the concrete reaches a predetermined strength after pouring. Said unit members 1 are joined vertically by mortar as said unit members are placed on top of each other to form the cylinders, and vertical clamp rods 9 are passed vertically through holes 10 in said unit members and tensioned to solidify the unit cylinders t vertically. The through holes 10 for the vertical clamp rods 9 are formed beforehand in said unit members 1. The tensioning of said vertical clamp rods 9 to give prestress to said unit members 1 is carried out each time several stages (ex. 5 stages) of said unit members 1 are assembled vertically to secure vertical solidification of unit cylinders t at each predetermined height. Therefore, even if an external force is applied during construction as described later, the damage to the joints can be prevented. In the present invention, silo cylinders T with a desired height are solidified lengthwise and crosswise, with the inside of said silo cylinders T as main silo spaces m and the spaces formed among the adjacent silo cylinders T,T', . . . as sub silo spaces S.

In general, the silo cylinder T receives two forces, viz. an internal pressure due to the contents such as grain and an external force due to an earthquake, wind, etc. The internal pressure due to the contents such as grain acts as a horizontal and circumferential tensile force at right angles to the silo cylinder T. In the present invention, since the couplings 3 are mutually clamped by the horizontal clamp rods 6 as mentioned before, the respective transverse joints a of the four unit members 1 constituting the unit cylinder t can transmit such tensile force favorably, and therefore have very large resistance against the internal pressure due to the contents. As shown in FIGS. 4 and 5 if horizontal recesses 11 are formed in the end portions and couplings and open into said coupling space J, such recesses 11 and the concrete 7 filling them from space J can, in combination, transmit said tensile force more favorably. The external force due to an earthquake, wind, etc, acts as horizontal force on the silo cylinder T. Such horizontal force acts on the silo cylinder T as bending moment and on the longitudinal joints b between unit cylinders t as a horizontal shearing force. The bending moment on the silo cylinder T causes tensile force on one side and compressive force on the other in the silo cylinder T, but generally, concrete walls are weak in resistance to such tensile force and are liable to crack and to have low airtightness. In the present invention, since the adjacent silo cylinders T and T' are solidly combined by the reinforced concrete 7 in said coupling space J and the horizontal clamp rods 5 clamping said marginal members proper 4 and 4' through said coupling space J as mentioned before, the vertical shearing force caused by the external force in said longitudinal joints b can be favorably transmitted to the respective adjacent silo cylinders T and T'. Since the lengthwise and crosswise arranged silo cylinders T,T', . . . are substantially solidified, the whole moves as a unit in response to the external force, and therefore has large rigidity, small deformation and very large resistance against the external force. In this case, if vertical recesses 11' are formed in the end portions 4 and 4' and couplings 3 and 3' and open into said coupling space J, such recesses 11' and the concrete 7 filling them from space J can, in combination, transmit the vertical shearing force more favorably, thus improving said effect remarkably together with said horizontal clamp rods 5 and 6. Furthermore, in the present invention, since the unit cylinders t formed by joining the unit members 1 and then assembled vertically and sequentially and joined by the mortar 8 are clamped by the vertical clamp rods to provide prestress as mentioned before, the horizontal shearing force at said longitudinal joints b, too, is favorably transmitted, and the resistance to such shearing force is very large. In this case, if a groove 12 is formed along the top of said unit member 1 and a mating protrusion 13 is formed at the bottom so that an upper one will be engaged with a lower one with the mortar 8 therebetween for joining, as shown in FIG. 7, then the horizontal shearing force can be transmitted more favorably.

In the present invention, as described above, the coupling spaces J are formed between the adjacent unit cylinders t and t' by said end portions 4 and 4' and the couplings 3 and 3' and such adjacent unit cylinders t and t' are joined solidly by the reinforced concrete 7 in said coupling spaces J having the horizontal clamp rods 5 and 6 therein, while the unit cylinders t and t' are sequentially stacked, and the stacked unit cylinders t, . . . themselves are solidified by clamping by the vertical clamp rods 9. Therefore, as an important feature, they are substantially more solidified than the silo cylinders constructed monolithically by the sliding form method from the standpoint of dynamics and structure, and have very large strength as mentioned before.

The present invention can further have the means as shown in FIGS. 7a-7d. The groove 12 is formed in the top of said unit member 2 and the protrusion 13 corresponding to said groove 12 is formed on the bottom. Furthermore, inserts 14 for holding adjusting supports are provided at a plurality of positions on the upper and lower portions of said member 2. When a unit member 1 of the next higher stage is placed on a unit member 1 already connected in a unit cylinder t, the adjusting supports 15 are mounted on the unit member 1 by bolts threaded into the upper inserts 14 of the already connected unit member 1 and mounted on the next higher unit member 1 by bolts threaded into the lower inserts 14 of the next higher unit member 1, and a bolt 17 with an adjusting nut 16 thereon is vertically mounted on each of the adjusting supports 15 mounted on the upper inserts 14, as shown in FIG. 7a. Each of said adjusting supports 15 on the next higher unit member 1 is supported by the adjusting nut 16 positioned on the upper portion of said bolt 17, to temporarily support the next higher unit member 1 at a position higher than the final joining position, as shown in FIG. 7b, and to adjust the horizontal position thereof. Then, mortar 8 is placed in said groove 12 of said already connected unit member 1, and the adjusting nuts 16 are lowered, to cause the protrusion 13 on the bottom of said next higher unit member 1 engage in the groove 12 of said already connected unit member 1 with the mortar 8 therebetween for joining the unit members. This provides means for making it possible that even silo cylinders T which are difficult to erect and repair can be constructed with very high accuracy, since slabs, etc, are not used intermediately, unlike precast concrete buildings in general. A gasket 18 can be mounted on one of the opposed faces of the members 2 outside said groove 12, and the gasket 18 serves both as a mold to prevent leakage of the mortar 8 outside the unit cylinder 1 and also as an airtightness means after joining of the unit members.

The present invention can also have means for suspending and supporting scaffold means as shown in FIGS. 8a-8d. Inserts 19 for mounting suspending supports are provided at the upper portion of each unit member 2, and scaffolding frames F are suspended and supported in the spaces in the unit cylinders t, viz. main silo space m and in the spaces formed among the adjacent units, viz. sub silo spaces S by suspending supports 20 mounted on the inserts 19. In this arrangements, said scaffolding frames F are suspended from and supported by the supports 20 on the already connected unit cylinders 1, while the next higher unit cylinders 1 are joined, as shown in FIG. 8a, and then supports 20 are mounted on the next higher unit cylinders 1 and cables connected from said supports to the scaffolding frames F and the suspending members on scaffolding frames F are disconnected, as shown in FIG. 8b. The scaffolding frames F are moved upward one stage and the suspending members are connected to the supports 20 thereat, as shown in FIG. 8c. After all the unit cylinders 1 are completely joined, said scaffolding frames F are fixed to the upper parts of the top unit cylinders 1, as roof frames, and roof slabs are placed on such roof frames. Thus, the construction can be executed very simply. With this means, the raising of the scaffolding frames F and the lifting of the unit cylinders 1 are by cranes, and the scaffolding frames F have only one stage, but as an alternative, scaffolding frames F with two working floors 21 and 22 corresponding to upper and lower stages may be used as shown in FIGS. 9a and 9b. In this case, the joining to an already assembled first unit cylinder t of a next higher unit cylinder t is carried out from the working floor of the upper stage 21, while the working floor 22 of the lower stage is supported by the suspending supports 20 mounted in the inserts 19 of the already assembled unit cylinder t one stage below said first unit cylinder t, as shown in FIG. 9a, and after said second unit cylinder t is joined to said first unit cylinder t, the hooks 23 of lifters I mounted on the scaffolding frame F are hung on the top of said second unit cylinder t as also shown in FIG. 9a. Then after the suspending supports 20 are released, the scaffolding frame F is raised by said lifters I one stage higher, and the position of said suspending supports 20 is changed to the inserts 19 in said first unit cylinder t, as shown in FIG. 9b. In this way the lengthwise and crosswise arranged unit cylinders are assembled while the scaffolding frames F are raised stage by stage. On the upper stage working floor 21, the unit members 1 constituting the unit cylinder t are joined as described above, and on the lower stage working floor 22 the clamping by the horizontal clamp rods 5 and 6 and joint treatment are carried out. Since different operations can be carried out simultaneously on the upper and lower stage working floors 21 and 22 in this way, the time normally to allow for the generation of sufficient strength of the concrete 7 and the mortar 8 can be saved. Therefore, the construction can be carried out faster, which is an advantageous effect of this aspect of the invention. In addition, since the scaffolding frames F are raised without using a heavy machine such as crane, but rather by the lifters I set in the scaffolding frames F themselves, safety and economy are promoted.

In the present invention, as described above, using precast concrete members as unit component members, silo cylinders are constructed lengthwise and crosswise from said unit members, to form a silo complex with the silo cylinders as main silo means and the spaces formed among the adjacent silo cylinders as sub silo means. Particularly, in the present invention, the unit members are joined lengthwise, crosswise and vertically in a very simple way, and such lengthwise, crosswise and vertical structure can be used to prestress the concrete. Therefore, the lengthwise and crosswise arranged silo cylinders are substantially solidified as regards dynamics and structure, and the circumferential tensile force caused by the internal pressure due to the contents such as grain and the horizontal and vertical shearing forces from an external force due to an earthquake, wind, etc, can be transmitted favorably, so that the silo cylinders are very solid. In the present invention, furthermore, since accurately dimensioned precast concrete members produced under close control are used as unit members, air does not leak through said unit members at all, and therefore, by providing sufficient airtight treatment of the longitudinal and transverse joints between such unit members, silo cylinders with very high airtightness can be easily constructed, which is a feature of the present invention. As for the transverse joints, reinforced concrete is provided in the coupling spaces formed between adjacent unit members in adjacent silo cylinders to solidfy and to provide a connection to the adjacent silo cylinders, and therefore airtightness is high. Furthermore, in the longitudinal joints, the provision of the gasket as described above makes it possible for good airtightness to be secured easily. Thus, by the present invention, one can easily construct silo cylinders with good airtightness. In addition, in the present invention, since all the work can be done from within the cylinders or in the spaces formed among the cylinders other than where molds and scaffolding are partially positioned outside, the construction is easy. Moreover, since the most of the silo cylinders is made of precast concrete produced in the factory, it is possible to reduce the amount of field work, the number of workers required at a given time is not unlike that for the conventional sliding form method, etc, enabling the construction to be carried out at constant work volume and with a constant work force and allowing easy control, which is a further feature of the present invention. 

We claim:
 1. A precast concrete member for use in constructing a concrete silo complex having a plurality of side-by-side silos, said member having a quarter-cylindrical configuration for being arranged in end-to-end fashion to form a cylinder unit, said member further having radially outwardly projecting coupling elements integral therewith and extending the full height of said member, one of said coupling elements being disposed adjacent each end of said member and said member having an end portion extending from each of said coupling elements to the corresponding end thereof, said coupling element having an outer end surface adapted to face a like outer end surface of a coupling element on a member in a cylinder unit in an adjacent silo, whereby said coupling element and the end portion adjacent thereto, with the corresponding coupling element and end portion on the adjacent member in the cylinder unit and the coupling elements on the members of the cylinder unit of an adjacent silo, form a box-like space for receiving concrete, said coupling elements having means for receiving tie means extending across said box-like space between two adjacent coupling elements, and said marginal end portions having means for receiving tie means extending across said box-like space between the end portion and the end portion of the member in the adjacent silo.
 2. A precast concrete member as defined in claim 1 in which said member has a lower edge with means thereon for nesting engagement with the upper edge of a like member positioned below said member, whereby one of said members can be stacked on another member to form a silo of a pile of said cylinder units; and said member having means to receive vertically extending tie means for prestressing the thus stacked members.
 3. A precast concrete silo complex comprising: a plurality of side-by-side silos, each silo being constituted by a plurality of members each having a quarter-cylindrical configuration and arranged in end-to-end fashion to form a plurality of cylinder units, each member further having radially outwardly projecting coupling elements integral therewith and extending the full height of said member, one of said coupling elements being disposed adjacent each end of said member and said member having an end portion extending from each of said coupling elements to the corresponding end thereof, a plurality of said cylinder units being stacked on one another with said members vertically aligned to form the silo, each coupling element having an outer end surface facing a like outer end surface of a coupling element on a member in a cylinder unit in an adjacent silo, a coupling element and the end portion adjacent thereto together with a corresponding coupling element and end portion on the adjacent member in the cylinder unit and the coupling elements on the members on the cylinder unit of an adjacent silo forming a box-like space between each of the adjacent silos for receiving concrete; horizontal tensioned tie rods extending across each box-like space between coupling elements on adjacent members in a cylinder unit; further horizontal tensioned tie rods extending across each box-like space between end portions of members in adjacent silos; concrete filling said box-like spaces between each of the adjacent silos and being reinforced by said tie rods; and vertical tensioned tie rods extending through pluralities of said members in each silo which pluralities together constitute all of the members in said silos.
 4. A precast concrete silo complex according to claim 3 in which the surface of said coupling members on at least some of said members has a recess therein opening into the box-like space defined thereby and which recess is filled with concrete.
 5. A precast concrete silo complex according to claim 3 in which the surface of said end portions on at least some of said members has a recess therein opening into the box-like space defined thereby and which recess is filled with concrete.
 6. A precast concrete silo complex according to claim 3 in which the surface of said coupling members and said end portions on at least some of said members has a recess therein opening into the box-like space defined thereby and which recess is filled with concrete.
 7. A precast concrete silo complex according to claim 3 in which the top edge of each member has a groove therein and the bottom of the next higher member has a protrusion therein mating with said groove, and each member further has inserts therein for mounting adjusting supports thereon at a plurality of positions on the upper and lower portions of said member.
 8. A method of constructing a precast concrete silo complex comprising: precasting a plurality of members each having a quarter-cylindrical configuration and having radially outwardly projecting coupling elements integral therewith and extending the full height of said member, one of said coupling elements being disposed adjacent each end of said member and said member having an end portion extending from each of said coupling elements to the corresponding end thereof, arranging a plurality of said members in end-to-end fashion to form a plurality of cylinder units, stacking a plurality of said cylinder units on one another with mortar therebetween and with said members vertically aligned to form a plurality of side-by-side silos with each coupling element having an outer end surface facing a like outer end surface of a coupling element on a member in a cylinder unit in an adjacent silo, a coupling element and the end portion adjacent thereto together with a corresponding coupling element and end portion on the adjacent member in the cylinder unit and the coupling elements on the members of the cylinder unit of an adjacent silo forming a box-like space between each of the adjacent silos, placing horizontal tie rods across each box-like space between coupling elements on adjacent members in a cylinder unit, placing further horizontal tie rods across each box-like space between end portions of members in adjacent silos, filling said box-like spaces between each of the adjacent silos with concrete, tightening said horizontal tie rods for prestressing the concrete, placing vertical tie rods through pluralities of said members in each silo, which pluralities together constitute all of the members in said silos, and tightening said vertical tie rods for prestressing said stacked cylinder units.
 9. A method as claimed in claim 8 further comprising, during stacking of said cylinder units, placing suspending supports on the upper portion of each of said members in the uppermost cylinder unit on a partically erected silo, suspending a scaffolding frame from said supports, stacking the next higher cylinder unit on the partially erected silo, placing further suspending supports on members in said next higher cylinder unit, and then raising the scaffolding frame to said further suspending supports and suspending the scaffolding frame therefrom, and thereafter repeating said steps for moving the scaffolding frame stage by stage upward in the silo being erected.
 10. A method as claimed in claim 9 further comprising, when the scaffolding frame reaches the top cylinder unit in the silo, fixing the scaffolding frame to the suspending supports on the top cylinder unit to serve as a roof frame, and placing roof slabs on said roof frame.
 11. A method as claimed in claim 8 further comprising, during stacking of said cylinder units, placing suspending supports on the members of the cylinder unit one below the uppermost cylinder unit on a partically erected silo, suspending the lower part of a two stage scaffolding frame from said supports, the scaffolding frame having an upper floor which, when the lower part is suspended from said supports, will be adjacent the upper edge of the said uppermost cylinder unit, stacking the next higher cylinder unit on the partically erected silo, placing further suspending supports on the members of the cylinder unit which was formerly the uppermost cylinder unit, hanging lift cable supports with lift cables depending therefrom over the top edge of the cylinder which is now the uppermost cylinder unit, using lifting means on said scaffolding framework and engaged with said lifting cables to lift said scaffolding framework to the level of said further suspending supports, and suspending said scaffolding framework from said further suspending supports. 